Buggy code:
public final class ActionRouter implements ActionListener { private static final Logger log = LoggingManager . getLoggerForClass ( ) ; private static final Object LOCK = new Object ( ) ; private static volatile ActionRouter router ; private Map < String , Set < Command > > commands = new HashMap < String , Set < Command > > ( ) ; private final Map < String , HashSet < ActionListener > > preActionListeners = new HashMap < String , HashSet < ActionListener > > ( ) ; private final Map < String , HashSet < ActionListener > > postActionListeners = new HashMap < String , HashSet < ActionListener > > ( ) ; private ActionRouter ( ) { } public void actionPerformed ( final ActionEvent e ) { } private void performAction ( final ActionEvent e ) { String actionCommand = e . getActionCommand ( ) ; try { try { GuiPackage . getInstance ( ) . updateCurrentGui ( ) ; } catch ( Exception err ) { ActionRouter . log . error ( ( ( ( ( "performAction(" + actionCommand ) + ")<seq2seq4repair_space>updateCurrentGui()<seq2seq4repair_space>on" ) + ( e . toString ( ) ) ) + "<seq2seq4repair_space>caused" ) , err ) ; JMeterUtils . reportErrorToUser ( "Problem<seq2seq4repair_space>updating<seq2seq4repair_space>GUI<seq2seq4repair_space>-<seq2seq4repair_space>see<seq2seq4repair_space>log<seq2seq4repair_space>file<seq2seq4repair_space>for<seq2seq4repair_space>details" ) ; } for ( Command c : commands . get ( actionCommand ) ) { try { preActionPerformed ( c . getClass ( ) , e ) ; c . doAction ( e ) ; postActionPerformed ( c . getClass ( ) , e ) ; } catch ( IllegalUserActionException err ) { String msg = err . getMessage ( ) ; if ( msg == null ) { msg = err . toString ( ) ; } Throwable t = err . getCause ( ) ; if ( t != null ) { String cause = t . getMessage ( ) ; if ( cause == null ) { cause = t . toString ( ) ; } msg = ( msg + "\n" ) + cause ; } JMeterUtils . reportErrorToUser ( msg ) ; } catch ( Exception err ) { <START_BUG> ActionRouter . log . error ( "" , err ) ; <END_BUG> } } } catch ( NullPointerException er ) { ActionRouter . log . error ( ( ( ( ( "performAction(" + actionCommand ) + ")<seq2seq4repair_space>" ) + ( e . toString ( ) ) ) + "<seq2seq4repair_space>caused" ) , er ) ; JMeterUtils . reportErrorToUser ( ( ( "Sorry,<seq2seq4repair_space>this<seq2seq4repair_space>feature<seq2seq4repair_space>(" + actionCommand ) + ")<seq2seq4repair_space>not<seq2seq4repair_space>yet<seq2seq4repair_space>implemented" ) ) ; } } public void doActionNow ( ActionEvent e ) { } public Set < Command > getAction ( String actionName ) { } public Command getAction ( String actionName , Class < ? > actionClass ) { } public Command getAction ( String actionName , String className ) { } public void addPreActionListener ( Class < ? > action , ActionListener listener ) { } public void removePreActionListener ( Class < ? > action , ActionListener listener ) { } public void addPostActionListener ( Class < ? > action , ActionListener listener ) { } public void removePostActionListener ( Class < ? > action , ActionListener listener ) { } protected void preActionPerformed ( Class < ? extends Command > action , ActionEvent e ) { } protected void postActionPerformed ( Class < ? extends Command > action , ActionEvent e ) { } private void populateCommandMap ( ) { } public static ActionRouter getInstance ( ) { } }

Fix:
ActionRouter . log . error ( ( "Error<seq2seq4repair_space>processing<seq2seq4repair_space>" + ( c . toString ( ) ) ) , err ) ;